Field of the Invention
The present invention relates to display control technology in a case where electronic zoom is performed in an image capturing apparatus.
Description of the Related Art
Conventionally, in the case where a captured image or an image transmitted from outside is displayed in real time, there is an issue of it being difficult to track and display the motion of a fast subject when the timing for display is delayed relative to the timing for image capture or image reception. In response to this issue, technology has been proposed that reduces the delay in timing for display (display delay) with respect to the input of an image.
For example, Japanese Patent Laid-Open No. 2012-222643 discloses technology for displaying a transmitted image with little delay. The following processing is performed in Japanese Patent Laid-Open No. 2012-222643. That is to say, a first calculation unit calculates an allowable delay time that denotes a delay time that is allowable when writing cannot be ended within a predetermined required time from the writing start time at which image writing starts. A second calculation unit calculates the minimal required time needed from the writing start time of the image written with a delay time that is less than or equal to the allowable delay time until the timing for display at which display of the image starts. A comparison unit compares the allowable delay time and the required time, and a display adjustment unit adjusts the timing for display based on the comparison results from the comparison unit. Then, a display control unit causes the image to be displayed in synchronization with the adjusted timing for display. Thus, such processing reduces the display delay.
Also, technology regarding overtake control is proposed as a memory access method that reduces display delay. In overtake control, memory access control is performed by applying a predetermined delay amount so that the readout of data does not overtake the writing of data to the same memory region. Accordingly, it is possible to reduce the delay amount caused by accessing the memory.
For example, in Japanese Patent Laid-Open No. 2003-323333, in a case where data is written to and read out from the same memory region, a predetermined delay amount is applied such that the readout of data does not overtake the writing of data, and if the two processes are not within a predetermined range, an access alarm is output and the readout is temporarily stopped. Accordingly, control is performed such that readout does not overtake writing.
In a case where capture, recording, and live-view display of moving images is performed with the image capturing apparatus, there is a need to maintain a fixed frame rate for image capture, recording, and live-view display. For example, in the case of capturing an object in which the size, location, or the like changes over time, if the frame rate of live-view display changes, smooth motion of the recorded images and the subject on the live-view screen is inhibited. For this reason, there is a possibility that the recorded image and the live-view image will appear to be unnatural. In Japanese Patent Laid-Open No. 2012-222643, a reduction in display delay is realized by adjusting the timing for display, but in the case where fixed frame rates are to be maintained for the above-described reasons, it is difficult to apply the technology disclosed in Japanese Patent Laid-Open No. 2012-222643.
Also, in a case where electronic zoom is used to display an enlarged portion of an image during image capture, a partial region of a written image is cut out and read out. For this reason, if data is written to and read out from the same memory region in the case where electronic zoom is used, there are cases where the timing at which readout is possible is later than in the case where electronic zoom is not used. In the case where this delay exceeds the predetermined delay amount between the timing for writing and readout set by the normal overtake control technology, there are cases where the live-view display is unstable. In other words, there are cases where a portion of the image is not in time for updating of the frame and the image read out for the previous frame is displayed for two frames, and thus there are cases of the quality of the live-view display being impaired.